1816991 has 4 divisors (see below), whose sum is σ = 1982184. Its totient is φ = 1651800.

The previous prime is 1816987. The next prime is 1817009. The reversal of 1816991 is 1996181.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1816991 - 2² = 1816987 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1816901) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 82580 + ... + 82601.

It is an arithmetic number, because the mean of its divisors is an integer number (495546).

2^1816991 is an apocalyptic number.

1816991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1816991 is a deficient number, since it is larger than the sum of its proper divisors (165193).

1816991 is a wasteful number, since it uses less digits than its factorization.

1816991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165192.

The product of its digits is 3888, while the sum is 35.

The square root of 1816991 is about 1347.9580854018. The cubic root of 1816991 is about 122.0255925885.

The spelling of 1816991 in words is "one million, eight hundred sixteen thousand, nine hundred ninety-one".